Problems of enhanced scan volume and increased readability of barcodes held at different orientations to a scanner are common to all barcode scanners (single and dual aperture scanners). Although these problems have been best addressed by the use of dual aperture scanners, even these scanners produce scan patterns with gaps in item coverage. These gaps generally increase as the item is moved away from an ideal position in the center of the scan volume.
Commonly assigned U.S. Pat. Nos. 5,229,588, 5,684,289, and 5,886,336 disclose a typical dual aperture optical scanner. The scanning light beams from a laser diode pass through substantially horizontal and vertical apertures to provide more item coverage than a single aperture scanner.
Furthermore, in an effort to increase item coverage, optics designers are increasing the number of scan lines, line length, and scan angles by increasing the number of lasers and pattern mirrors in the scanner. The addition of these components consequently increases cost.
Therefore, it would be desirable to provide an optical scanner which is not only capable of reading a bar code label on any one of six orthogonal surfaces of an item oriented at right angles to the scanner, but is also capable of reading the bar code label if it is located on any intermediate surfaces between those orthogonal surfaces.
The complexity of dual aperture scanners will be described in order to illustrate another advantage of the present invention, which is the simplicity and corresponding ease of construction of the scanner.
As will be illustrated in more detail below, with reference to FIGS. 1 to 6, present day scanners comprise, a laser assembly, spinner assembly, collection optics, pattern mirrors, detector assembly, electronics, a window and scanner housing which contains all the individual assemblies. In operation, the laser beam intercepts the polygon spinner rotating about a single axis and is subsequently scanned in a single plane towards a set of pattern mirrors which reflect the individual scan lines out the window and onto a barcode. The laser energy is then reflected off of the barcode and a portion is gathered by the collection optics and focused onto the detector generating a signal to be decoded by the electronics. The positions at which the scan lines exit the window are static, and are contained in a relatively small portion of the hemispherical volume available outside and adjacent to the window (FIG. 6). Consequently, the readability of barcodes is limited to certain orientations within that small scan volume